Preheat your oven to 375°F and grease a 13x9-inch baking dish to prevent sticking.
In a large mixing bowl, combine the cream of chicken soup, mayonnaise, and Worcestershire sauce until smooth.
Fold in the cooked chicken, broccoli, and chopped onion, making sure the mixture is evenly coated.
Pour the mixture into the prepared baking dish and spread it out evenly. Sprinkle the shredded cheddar cheese over the top.
Cover the dish with aluminum foil and bake for 20 minutes to let the flavors meld together.
While the base bakes, separate the biscuits and cut each one in half. Remove the casserole from the oven and arrange the biscuit halves, cut side down, over the hot mixture.
In a small bowl, whisk together the eggs, sour cream, celery seed, and salt. Pour this mixture evenly over the biscuits.
Return the casserole to the oven and bake, uncovered, for an additional 28-32 minutes, or until the biscuits are golden brown and baked through.